Vehicles, such as, for example, motor vehicles, are typically provided with a suspension system to reduce or damp the transmission of vibrations from the road surface upon which the vehicle is traveling to the occupants of the vehicle. Such suspension systems frequently comprise one or more shock absorbers, spring struts and/or springs. Coil springs, for example, are commonly used within the damper system of a vehicle suspension.
A coil spring may, for example, be seated on a spring plate such that at least a portion of a last coil of the spring rests on the spring plate. In this manner, when force is applied to the coil spring, such that the coils of the spring are compressed along a longitudinal axis of the spring, the contact area between the spring plate and the last coil of the coil spring (i.e., resting on the spring plate) enlarges. Also, coil springs have a tendency to curve or bend slightly under compression. In other words, a coil spring will bend relative to its longitudinal axis when the coils of the coil spring are compressed along the longitudinal axis. Due to the axial force and the bending of the coil spring, the size of the contact area changes and/or a relative movement occurs between the spring plate and the last coil of the coil spring resting on the spring plate. This phenomenon of a moving contact boundary is, for example, often referred to as rolling contact.
An elastic insert, or spring isolator, is also generally inserted between the coil spring and the spring plate to damp the transmission of vibrations to the coil spring and the occurrence of noise between the parts. Because of the abovementioned relative movement between the coil spring and the spring plate or spring isolator (i.e., rolling contact), foreign particles, such as, for example, particles of dirt, sand grains, or other particulate debris may penetrate into the contact area (i.e. of changing size) between the last coil of the coil spring and the spring plate or spring isolator. Because of the frequently recurring movements of the coil spring during operation of the wheel suspension, such ingress of debris can lead to abrasion of the paint coating normally applied to the coil spring. When the paint coating has been completely abraded from the coil spring, corrosion can occur on the then exposed metal of the coil spring, which may lead to premature failure of the coil spring or require premature replacement of the coil spring.
It may, therefore, be advantageous to provide a spring isolator for a wheel suspension of a vehicle in which the risk of corrosion of the coil spring, due to movement of the coil spring relative to the spring isolator during operation of the vehicle suspension, is either absent or at least reduced. It may also be advantageous to provide a spring isolator that sufficiently damps the transmission of vibrations from the spring plate to the coil spring, and the occurrence of noise at the coil spring and spring plate.